The biochemistry of the barrier between retinal and/or choroidal blood and the vitreous body (the B-V barrier) will be studied in vivo in laboratory animals. Alterations in the magnitude of transfer coefficients for substances entering the vitreous body across the B-V barrier: induced by drugs or metabolic inhibitors. The drugs or inhibitors will be used either systemically or topically to one eye of an animal. The test substances whose transfer coefficients will be measured will include radioactive cations, anions, some amino acids and other substances which are either transported or can be used to identify the transport function of the B-V barrier. In general the test substances used will be radioactive labels (used in tracer amounts) of substances normally present in the blood and the eye. Radioactive labeled drugs will be used to correlate intraocular localization with drug effect. The data obtained should be useful basic data on the B-V barrier important both to clinicians interested in glaucoma and the "internal milieu" of the retina and vitreous body and to others interested in eye physiology.